1996 E350 5.8L 351 misfire
Member
Joined: May 2025
Posts: 38
Ordered pcm
I just came back in town from a trip. Every time in the morning now it will take a bit longer to start than usual. Then again buck a bit at stoplights. Drives perfect in every other way.
after driving 3 hours and leaving fwy, still slight hesitation from stop. Went to park on a hill, and lost all power going backwards. Struggled to keep it running hearing knocking and misfire sounds. Parked and 30 minutes later everything working great again. Should get new pcm next week.
after driving 3 hours and leaving fwy, still slight hesitation from stop. Went to park on a hill, and lost all power going backwards. Struggled to keep it running hearing knocking and misfire sounds. Parked and 30 minutes later everything working great again. Should get new pcm next week.
Senior Member
Joined: Jun 2010
Posts: 16,584
Did the diagnosis include plans for what to replace next after the replacement PCM is installed and the problem is still there?
The PCM can cause problems like that , but we always try the simple things first.
A good move would be to have the system checked for codes and which cyl(s) are misfiring.
A lot of cheaper things can cause/contribute to a misfiring problem.
If it is always the same cyls,we concentrate on those cyls. If,,, is different cyls, we look for things that can affect `all cyls.
Can we ask how it was determined to be the PCM ?
The PCM can cause problems like that , but we always try the simple things first.
A good move would be to have the system checked for codes and which cyl(s) are misfiring.
A lot of cheaper things can cause/contribute to a misfiring problem.
If it is always the same cyls,we concentrate on those cyls. If,,, is different cyls, we look for things that can affect `all cyls.
Can we ask how it was determined to be the PCM ?
Member
Joined: May 2025
Posts: 38
Did the diagnosis include plans for what to replace next after the replacement PCM is installed and the problem is still there?
Pay another shop to diagnose it more, costing more than the new pcm.
The PCM can cause problems like that , but we always try the simple things first.
Yes tried all things as listed.
A good move would be to have the system checked for codes and which cyl(s) are misfiring.
no codes
A lot of cheaper things can cause/contribute to a misfiring problem.
I would have hoped.
If it is always the same cyls,we concentrate on those cyls. If,,, is different cyls, we look for things that can affect `all cyls.
I don't understand.
Can we ask how it was determined to be the PCM ?
Pay another shop to diagnose it more, costing more than the new pcm.
The PCM can cause problems like that , but we always try the simple things first.
Yes tried all things as listed.
A good move would be to have the system checked for codes and which cyl(s) are misfiring.
no codes
A lot of cheaper things can cause/contribute to a misfiring problem.
I would have hoped.
If it is always the same cyls,we concentrate on those cyls. If,,, is different cyls, we look for things that can affect `all cyls.
I don't understand.
Can we ask how it was determined to be the PCM ?
Senior Member
Joined: Jun 2010
Posts: 16,584
If you are checking for low Vref , might be a good move to start at the PCM and check what you have there, why ?
If you have it there and not where the scan tool is getting it, you may not need a PCM..
Among the could bees, if any component that is supplied Vref, is shorted, it can pull down that Vref.
This is where some good diagnostics come in handy. A schematic diagram would help there !
If you have it there and not where the scan tool is getting it, you may not need a PCM..
Among the could bees, if any component that is supplied Vref, is shorted, it can pull down that Vref.
This is where some good diagnostics come in handy. A schematic diagram would help there !
Member
Joined: May 2025
Posts: 38
Do you have a source for the schematic? Do you have references available for me here in Torrance ca? My thinking is if a short or problematic part were at play, the vref wouldn't be exactly 2.50 up to 2.51. Instead be fluctuating. A bad tfi module could also be the problem. If i don't change it, I'll never know. Unless you can help with sources.
Member
Joined: May 2025
Posts: 38
Last edited by MacGyverMU; May 15, 2025 at 11:37 PM.
Member
Joined: May 2025
Posts: 38
Possibly solved
The person who posted saying new parts can be defective was correct. Turns out the maf from oreilly was defective. Found a new oem finally and replaced. Replaced pcm, fuel pressure regulator. After 100 miles got po300, same issues and vref still showing 2.5v. Finally checked the new fuel pumps pressure again and now it's showing 23lbs. Should be 45 so it seems to be defective as well. Should know by next week.
Senior Member
Joined: Jun 2010
Posts: 16,584
Speaking for myself after many years of experience I have yet to receive a defective part from a dealership. Sometimes we can't always do that, but learned a lot the hard way..
There are a lot of good aftermarket suppliers out there. Next time you purchase a part from an aftermarket supplier, or discount automotive supply (place) check where the part was made BEFORE you buy it. A lot of places are supplying JUNK IMPORTED parts. Many are defective right out of the box.
.It has to be fun when you buy a defective electrical part and they won't exchange electronic/electrical parts.
There are a lot of good aftermarket suppliers out there. Next time you purchase a part from an aftermarket supplier, or discount automotive supply (place) check where the part was made BEFORE you buy it. A lot of places are supplying JUNK IMPORTED parts. Many are defective right out of the box.
.It has to be fun when you buy a defective electrical part and they won't exchange electronic/electrical parts.